Prep the pan: Line an 8x8-inch square pan with parchment, leaving overhang for easy lifting. Lightly spray the sides.

Heat the oven: Preheat to 325°F (163°C). A moderate temperature prevents cracks and keeps the filling silky.

Make the crust: In a bowl, mix 1 1/2 cups almond flour, 3 tablespoons granulated keto sweetener, a pinch of salt, and 5 tablespoons melted butter. Stir until it looks like damp sand.

Press and par-bake: Press the crust firmly and evenly into the pan. Bake for 10–12 minutes until lightly golden at the edges. Let it cool for 5 minutes.

Beat the cream cheese: In a large bowl, beat 16 ounces softened cream cheese on medium speed until smooth and fluffy—about 1–2 minutes. Scrape the bowl.

Sweeten and flavor: Add 1/2 cup granulated keto sweetener and beat until dissolved and creamy. Mix in 2 teaspoons vanilla extract (and 1 teaspoon vanilla bean paste if using) plus 1 teaspoon lemon zest if desired.

Add sour cream: Beat in 1/2 cup sour cream until fully combined. The mixture should look glossy and smooth.

Add eggs gently: Add 2 large eggs, one at a time, mixing on low until just combined. Do not overbeat. Overmixing traps air and can cause cracks.

Fill the pan: Pour the filling over the crust. Smooth the top with an offset spatula and tap the pan gently to release air bubbles.

Bake low and slow: Bake at 325°F for 28–35 minutes. The edges should be set, and the center should have a slight jiggle, like gelatin.

Cool gradually: Turn off the oven, crack the door, and let the bars sit for 10 minutes. Move to a rack and cool to room temperature.

Chill to set: Cover and refrigerate for at least 4 hours, preferably overnight. This step firms the texture and deepens the flavor.

Slice cleanly: Lift the slab out by the parchment. Use a sharp knife wiped clean between cuts to make neat squares.